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FAN SUCTION CAPACITY FOR DOWNDRAFT TABLE

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enzed
Posts: 61
Joined: Mon Aug 17, 2015 1:44 pm

FAN SUCTION CAPACITY FOR DOWNDRAFT TABLE

Postby enzed » Mon Sep 26, 2016 2:52 pm

What would be the recommended suction capacity (cfm) of an extractor fan fitted to a downdraft table having overall dimensions of 5 feet by 4.8 feet (essentially a 4 x 4 ft table)?

Thanks,
enzed

jawslandshark
Posts: 33
Joined: Tue Mar 01, 2016 4:41 pm

Re: FAN SUCTION CAPACITY FOR DOWNDRAFT TABLE

Postby jawslandshark » Tue Sep 27, 2016 11:26 am

Can Max Fan Mixed Flow Inline Fan, 12-Inch 1709 Cubic Feet Per Minute

Look this fan up on Amazon, you could get by with the 10-inch for the size of your table but the 12 will be awesome. Depending on how you set up the downdraft it will keep your shop smoke free. Use welding blankets for areas that a sheet does not cover over the slats.

enzed
Posts: 61
Joined: Mon Aug 17, 2015 1:44 pm

Re: FAN SUCTION CAPACITY FOR DOWNDRAFT TABLE

Postby enzed » Wed Sep 28, 2016 9:50 am

Hello jawslandshark,

Thank you very much for the valuable information. I conclude from your second sentence that there are different ways of setting up the downdraft, in which case a few photos of how you did it, plus a photo or two of how you use the welding blankets, would be very useful.

Thanks again and best wishes,
enzed

jawslandshark
Posts: 33
Joined: Tue Mar 01, 2016 4:41 pm

Re: FAN SUCTION CAPACITY FOR DOWNDRAFT TABLE

Postby jawslandshark » Wed Sep 28, 2016 2:49 pm

Hope this helps, hard to see with the slats in but the panels are welded in on the top sides and then come together somewhat to a point down below with some air flaps on either end. The drops collect in the center then and can be cleaned out with a magnetic pickup handle. I cut lots of one off pieces so if a full sheet is not on the table I just drape a welding blanket on the top sides of the slats. I can leave the front of the table open and still get great suction.

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enzed
Posts: 61
Joined: Mon Aug 17, 2015 1:44 pm

Re: FAN SUCTION CAPACITY FOR DOWNDRAFT TABLE

Postby enzed » Thu Sep 29, 2016 12:01 am

Thank you very much jawslandshark, I appreciate you taking and posting the photos. Yes, together with your added description, they certainly do help in seeing how you dealt with this matter. Best wishes, enzed.

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see&see
Posts: 182
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Location: Minden, Nevada

Re: FAN SUCTION CAPACITY FOR DOWNDRAFT TABLE

Postby see&see » Fri Sep 30, 2016 11:11 am

I'm adding a 5 x 10 table and I've had good success using a 20" duct on the side panel of a 4 x 4 table and a 3000 cfm wall mounted fan. I have a couple shops, one at home and another commercial shop and I've bought a lot of fans in my day. I just happened to find J & D Manufacturing one day on the net. They are a USA company have the China wall mount fans beat by a mile IMO including price. The link below is a 3 phase model I ordered but they also sell a single phase fan in the same frame. The model in the link is around 6000 CFM at 0.10 SP I just ordered for the 5 x 10 table.

https://www.amazon.com/gp/product/B00XJ ... UTF8&psc=1

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PlasmaCam DHC2 4 x 4 & Sampson 510 Snap 'n Cut w/Safety Switch Interface Hypertherm 85 & 45XP

enzed
Posts: 61
Joined: Mon Aug 17, 2015 1:44 pm

Re: FAN SUCTION CAPACITY FOR DOWNDRAFT TABLE

Postby enzed » Sat Oct 08, 2016 10:27 am

Thank you for the useful information see&see. Best wishes, enzed

msimpson99
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Re: FAN SUCTION CAPACITY FOR DOWNDRAFT TABLE

Postby msimpson99 » Wed Oct 12, 2016 10:30 am

What hose are you using? How does it hold up? I'm looking at doing a 12" system for a smaller table.

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see&see
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Location: Minden, Nevada

Re: FAN SUCTION CAPACITY FOR DOWNDRAFT TABLE

Postby see&see » Wed Oct 12, 2016 7:20 pm

I used 20" flexible tin foil duct in a 25' section. (link below) I put a baffle in front of the inlet under the grate to keep hot metal from landing in the duct. You only need 3 or 4 feet of duct each time you change it from sparks landing inside. Changed about once every 6 months on average. They also have other sizes of duct..

https://www.comfortgurus.com/flexible-d ... results=59

With 3000 cfm and 20" circumference of suction duct the noise is hardly noticeable. I sometimes forget and leave the fan going it's so quiet. Smaller duct needs more velocity so the trade off is higher fan speed and noise to move the same amount of air.
PlasmaCam DHC2 4 x 4 & Sampson 510 Snap 'n Cut w/Safety Switch Interface Hypertherm 85 & 45XP

enzed
Posts: 61
Joined: Mon Aug 17, 2015 1:44 pm

Re: FAN SUCTION CAPACITY FOR DOWNDRAFT TABLE

Postby enzed » Mon Oct 24, 2016 12:18 pm

Hi see&see,
Firstly, my apology for taking so long to reply, I just haven't managed to do so sooner. Thank you for your contribution as well. You seem to confirm what others have also stated, namely that a suction of 3000 cfm and a duct of 20" does the trick on a 4'x 4' table. Best wishes, enzed.


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